WASHINGTON—Seeking to keep a fragile global recovery on track, the International Monetary Fund on Tuesday called on countries that can afford it—including the U.S. and Britain—to slow the pace of their austerity measures.

The fund warned that "overly strong" belt-tightening in the U.S. will slow growth this year. Across-the-board government spending cuts, known as the sequester, were the "wrong way" to shrink the...